White people - depending on your definition, I mean pale-skinned Northern Europeans - are adapted to live north of about 45 degrees.

Obviously they live lots of other places now, but evolution is slow to catch up.

If you drive through France for a day, you can literally see the change from north to south, "could be Dutch" in the far north to "could be Spanish" in the south. Of course lots of people move around but I'm talking about averages.